Vol 13, No 7 (2013) / Xin

A revised rotation curve of the Milky Way with maser astrometry

Xiao-Sheng Xin, Xing-Wu Zheng


We reconstruct the rotation curve of the Milky Way using the new trigonometric parallax and proper motion data for masers in 43 high-mass star-forming regions obtained by VLBI, as well as the existing data from the literature, based on a new set of galactic constants (R0, Θ0) = (8.4 kpc, 254 km s−1) measured by Reid et al. The revised rotation curve of the Milky Way is almost flat or slightly rising in the region from about 6 to 15 kpc. The rotation velocities within 5 kpc of the Galactic center, as determined by VLBI, differ from those obtained by measurement of the HI- and CO-line tangent velocities. We fitted the revised rotation curve arising from three mass components: the bulge, disk and dark matter halo. The total mass of the Milky Way is found to be 2.3×1011M (20 kpc). This is about 10% larger than that from Sofue et al, and is comparable with the mass of M31, 3.4×1011M (35 kpc), given by Carignan et al. The limited accurate observational data, especially the VLBI data, do not permit a fully satisfactory fit to the rotation curve. The extensive parallax and proper motion data that will be produced by the Bar and Spiral Structure Legacy Survey project in the next few years should lead to considerable progress in understanding the rotation curve and dark matter halo of the Milky Way.


Galaxy: structure — Galaxy: bulge — Galaxy: disk — Galaxy: halo — dark matter — masers

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